Packing for vapor and liquid contacting apparatus



F. L. MELVILL 2,405,593 PACKING FOR VAPOR AND LIQUID CONTACTINGAPPARATQSFiled Feb; 4, 1944 w w 0 o ATTORNEY Patented Aug. 13, 1946 UNITED STATESPATENT OFFICE PACKING FOR VAPOR AND LIQUID CONTACTING APPARATUS FrancisL. MeIvilI, New York, N. Y.

Application: February 4, 1944, Serial No. 521,049

Z Claims. 1,

This invention. relates topacking for gas or vapor and liquidcontacting, apparatus. Although the invention has a wide range ofutility, itis particularly useful in connection with contactingapparatus employed for the absorption, cooling, drying, cleansingor-h-umidifying of. gases, for the evaporation, cooling or heating ofliquids, or for reaction purposes. Such'apparatus may, for example, takethe form of fractionating towers, scrubbers, cooling towers and thelike. In such apparatus, a. packing is usually employed for efiectingintimate contact between the .descending liquid and the ascending gas orvapor. As used herein and in the claims, the term gas includes vaporwithin its scope.

The invention provides a novel. packing for gas and liquid contactingapparatus which; avoids the presence of unequal. gas or liquid passagesand prevents channeling or segregation of the flowing gas in open spacesand of the liquid along surface areas, with the result that atanycross-section of the packing at right angles to the general direction ofcountercurrent flow of the liquid. and gas, the. composition of. theliquid. and gas aresubstantially uniform.

The invention also provides a new and improved packing of the generalcharacter described; which feeds: and spreads out the liquid evenly in athin filmand in a regular predetermined symmetrical manner as itdescends. in a treating chamber, so that even. distribution of theliquid throughout the flow area of the chamher is aiiorded, whichprovides themaximum of effective (i. e., wetted) surface area per unitof packing space, ofiers aminimumof: resistance 1 to the passage of theascending gas, andv afiords a maximum of intimacy of contact and inter--action between liquid and gas, so that equilibrium between the fluid ineither phase immediately adjacent to the inter-face and the main bulk ofthe fluid comprising the phase is rapidly attained.

The invention further provides apackingoi the general characterdescribed, which comprises a series of simple, comparatively inexpensiveelements requiring little or noshaping, and which can be easily andexpeditiously assembled.

In carrying out. the features of the invention, packing elements ofsmall cross-section. and desirably in the form of rods, wires or tubes,are arranged to form a network of. predetermined. pattern, and to definecourses along which the liquid. is directed in. the form of thin exposedstreams encircling the elements. The packing elements are desirablystraight and are. latticed along the elements diverging fromsaidiintersections. The liquid. flowing down a singleel'ement of the.packing isregularly mixed. with liq.- uid flowing down an adjacentelement. of the packing, and the resulting mixtureis thenredistributedamong elements diverging from. the

mixing zone. each; of these. redistributed streams carryingsubstantially the same aliquot part of the liquid reaching. the mixing.zone.- from. above.

The nature of the invention. be. apparent from the. followingdescription when considered in connection with the accompanying drawingforming. a part thereof,.and inwhich:

Fig. 1- is a fragmentary axial vertical section, somewhat diagrammatic,oi a gas and liquid; contacting' device containing a packing embodyingthe invention;

Fig. 2 is a transverse section, somewhat diagrammatic, of. thecontacting device, taken. on line 2-2 of. Fig. .1;

Fig. 3' is a view in elevation of one of. the packing elements: prior toassembly;

Fig. 4. is: a view in elevation. showmg a pair of packing elementsassembled to fijrman. intersecting liquid mixing and. distributing zone;

Fig. 5 is a. view in. elevation of. a portion of the packing of Figs. 1.and 2. but. shown. on a. larger scale; and

Fig. 6 is a horizontal section 'ofthe packing. taken on line. 66 oi Fig.5.

Referringtoz Figs. 1 and 2 of theadrawi'ng. the gas and liquid:contacting device is shown com.- prising avertical cylindrical. columnor tower l0. containing the packing ll of the invention. The. gas to be:contacted is delivered tothe lower portion. or the tower l0 below thepacking U, and flows upwardly through the packing, while liquid. is;fed. to the uppenportio-n of the tower above the packing, and flowsdownwardlythrough the packing in thin. streamsandin intimatecontact withthe ascending gas in. a manner'tobe described. The liquid is desirablydelivered. to the upper portion of the tower Ill and. over the packing Hinsuchscattered form asto be. spread substantially evenly over the topof the packing ll, so that the liquid is distributed substan 51 5 shownoccupying thecentralj portion of "the towerlil,"'while the diametricallyopposite side chordal sections 12 of the tower are m left vacant orunpacked. A pair of partition plates 13 on the straight or chordalsidesrespectively of the packing I prevent flow-into or out.

of the packing through the sides. The unpacked.

cal. The two layers 20 of elements 16 of each packing sheet H areinterconnected to form a sheet unit, as will be more fully set forth,and are latticed as described to define a series of quadrilateralstaggered meshes 22 large enough to prevent capillary filming of thedown flowing liquid across the meshes, but preferably as small aspossible having regard for the liquid gas load. The adjoiningsectionsofthe elements I16 forming the two upper sides of each ineshi? are ofequal length, and the adjoining sections of the elements forming the twolower sides of each .mesh are also of equal length, and are desirably ofthe same length as the two upper element spaces l2 of the tower I!) maybe sealed either at the bottom or the top in any .manner wellriknown inthe art to prevent by-pass flow through these spaces. The clearancebetween the arcuate peripheral portions of the packing H and thecorrespondingjwall of the tower l may be sealed bya'ny suitable means,as 'for example by means oflaye'rs Hof glass wool. f As a feature of theinvention, the packing ll cot prises alseries of slender elements l6which may be in'the form the like, and which are shown specifically assolid cylindrical rods. These'packing elements 16 are identical intransverse cross-sectional size and shape, ,and their surfaces are ofsuch material andjfinishjasto be substantially-wetted by the liquidundernorinal'operating conditions. For that purpose, the-packingelements 16 are desirably of material having the necessary finish toaff'ord the required wetting properties. These packing elements 1B are"of sufficient diameter so that they will have substantial rigidity. Forexample, packing elements one-tenth of an inch in diameter will besatisfactory, although'larger or smaller sizes may "be desirabledepending upon the circumstances of'use ofthe packing.

Although the packing elements l6 are shown in cylindrical'form, as farascertain aspects of the invention a're concerne'd, they may be of anysuitable symmetrical cross-sectional shape. For ex-. ample, the surfaceof the elements'fli may be n dea; fluted or 'otherwisetreated to form aregular pattern thereon: The groove may extend parallel to thelongitudinal axis of the elements l6, or may extend helicallyor intheform of a thread. Such'surfac'e grooving of the ele-: ments it maybeprovided to increase the liquid carryingca'pacity of; the rods. Also,instead, of using single rods-Wires orthe like, as far as certainaspectsof the invention are concerned each of the packing elements Itmay consist of multiple wires braided or helically twisted together, orlaid side by side; V i

The packing elements iii are arranged to form aplurality of-verticalunits or sheets IT in face tofalce contact, each comprising a series ofeleinents criss-crossed-to'define a plurality of liquid mixing anddistri uting junction zones 18; In the specific form'of theiriventionshown, each vertical packing sheet 11 comprises two inter facing layers2B of packing elements arranged in 'c riss cross fashion. The elementsit of one layer 2B-in'a p'acking sheet I! are equally spaced andarrangedobliquely'in parallel-in one vertical plane, and the elements ofthe other layer of the "s nse sheetare spaced the same distance apartand are similarly arranged obliquely in parallel iii-a ve ic'a pla e bitj extend in oblique directions reverse to those of the elements of thefirst layers'but atthesameinclination with the vertiof wires, tubes,flat strips or specifically shown as square in shape.

sections. The meshes 22 are advantageously in the form of equilateralparallelograms, and are The meshes 22 of each packing sheet I! arearranged in vertical rows with the vertice l8 of the meshes of each rowin vertical alignment, and the meshes of adjoining vertical rowsmedially staggered. This construction lends symmetry to the arrangement,and serves-to assure a more uniform mixing and distribution of theliquid in its-downward flow through the packing l l The elements H5 inthe two criss-crossed layers 20 of each packing sheet ll desirably areinterconnected at the intersections l8 of said element preferably bywelds 23. These welds 23 Y preferably are on the upper sides of theintersec- It will be understood that any number of these Welds 23maybe-formed according to the overall size of the packing sheets I! orthe size of the packing elements. For example, the welds 23 may beformed at each intersection 18, or at spaced intervals. Y

The lengths of the packing elements l6 vary according to the overallsize of the packing sheets I1, or the cross-sectional size of theelements. For example, in the smaller packing sheets, the elements 16may be made to extend integrally from edge to edge of the sheet, whilein the larger packing sheets, theelements, and especially the longerones, may consist of difierent sections positioned in axial abuttingalignment. These axially aligned elements 16 may be'butt-weldedtoethenif desired.-

lhe packing sheets I! as described are substantially identical as far asthe size and shape of their meshes 22 and the diameter of their elements16 are concerned, and are arranged verti cally in lateral face to facecontact with the elements of alternate layer 20 running in the sameoblique direction, to form the composite packing H. Thesepacking sheetsI! desirably are so arranged that the meshes 22 of one sheet are inhorizontal registry with the meshes of the other sheets, as shown inFigs.- 5 and'6. However, as far as certain aspects of the invention areconcerned, the packing sheets H may be relatively displaced vertically,so that the meshes 22 of one packing sheet I! are out of phase withthe'meshes of adjoining sheets. :For example, the meshes 22 of alternatepacking sheets ll' may be in hori-' zontal registry, while the meshes ofintervening packing sheets maybe in horizontal registry but mediallydisplaced with'respect tofthe' meshes of 76 the other sheets. Inthislatter' arrangement, the

vertices of the. meshes 22 of one packing sheet I! would be disposedcentrally with respect to the. meshesof adjoining sheets.

The packing sheets l1 may be interconnected together, or may berelatively displaceable vertically. This latter arrangement may bepreferred, where for example, it is desirable to vibrate some or the:sheets I]: edgewise with respect to others to promote turbulence in thefluid flow or to pre vent-clogging of the packing.

Inthe use of. the packing H, the liquid with. which it is. desired tocontact the ascending gases is delivered to the top section of thepacking as described, and is: divided into; a number of predeterminedexposed. streams which flow obliquely downwardly along the elements Itin regular zigzagcourses. The liquid fiowssubstantially evenly in: avseries of thin films over the. surfaces of the packing elements: in adirection generally counter to the direction of flow of the gas. Themaximum-of liquid surface thereby is exposed to the action of theascending gas. The liquid stream flowing down along a single element i=6of the packing ll merges at a juncture l8 with the liquid stream flowingdown an adjoining element. At this. juncture t8, the two streams arethoroughly intermixed, and the resulting mixture is then subdivided andredistributed equally between the elements diverging downwardly from thejuncture. Each of these diverging elements constitutes part of anotherpair of elements converging towards a juncture it, so that the two.diverging distributed streams merge and intermix with other adjoiningstreams, and then again become subdivided. This process is repeated sothat uniform mixing and distribution of the liquid in thin filmsthroughout the width oi'each packing sheet IT is assured. Also, sincethe packing sheets I! are in lateral face to face contact, the liquid inone sheet is not only distributed and mixed substantially uniformlythroughout the width of the sheet, but is also distributed andintermixedwith the liquid of adjoining packing sheets. in this manner,substantially uniform mixing and. distribution of the; liquid throughoutthe entire horizontal. section of the packing is assured.

If the flow along the various elements It is not. equal, the degree ofinequality will tend to becomeprog-ressively reduced due to the factthat each element will divide, or will tend to divide, the whole of theliquid reaching a given mixing zone [8 equally with its element partnerin that zone. This is. particularly important in the upper section ofthe packing I I, where the liquid feed may not be deposited uniformlyover the top of the packing. By the equalizing process described, thedistribution of the liquid under these conditions will become uniform inthe upper section of the packing H. Uniform distribution of the liquidwhen once attained near the top of the packing I I will persistto-thebottom thereof. The gas flows generally upwardly and tortuouslythrough the meshes 22 countercurrent to the liquid and contacts theexposed thin liquid films on the packing elements IS. The disposition ofthe meshes 2-2 insures the necessary turbulence to secure thoroughmixing, thus avoiding the loss of efhciency which results when gas atthe liquidgas interface is not mixed as rapidly as possible with themain bulk of the gas, and when other purely local conditions within thepacking ll tend to vary the composition of the gas across any section ofthe tower Ill. The velocity of the gas upwardly will be substantiallythe same at any point in any plane at rightangles to the generaldirecti'onof flow. Maximum intimacy of contact and maximum interactionbetween-liquid andgas is obtained, and equilibrium is rapidlyestablished between the material in either vapor or liquid phaseimmediately adjacent to'thei nterface: and the main bulk of the:material comprisingthe phase.

Orr any cross-section of the packing H at right angles to the, generaldirection of flow-oi the liquid and gasv the composition of the gas issubstantially the same and the composition of the liquid in itsconstituent streamsis substantially thesame. The pressure drop of theliquid passingthrough the packing I l and the amount of liquid retainedby the packing under normal operating conditions is comparatively low. Acomparatively long path of travel of the liquid passing through thepacking H is provided so that retention of the liquid for aperiod longenoughto assure the necessary saturation or interaction with the gas isassured.

Inasmuch as each of the elements extends in a downwardly inclined:direction from the inner wall. of the tower l0, liquid which reaches thewall by way of some of the elements will flow away from the wall by wayof other elements and thu-s will. tend to retain the liquid. in thepacking and prevent short circuiting. flow down the wall of thetower.

The velocity of the vapor vflowing upwardly through the packing: willcause or tend to cause the liquid on the elements to assume astreamlined or tear drop. shape suchas would present the minimumresistance; to the flow of' vapors and this, together with the surfaceeffects which become pronouncedv with thin film of liquid, will have theefiect of distributing: the liquid over the surfaces. of the elementswith a tendency for a major part ofthe liquid to flow down the upperpaits of the-elements, the amount of liquid so flowing. increasing with.increased vapor velocity. The effect of this is to insure the maximumexposure of the liquid to the' vapor and to facilitate the mixing of thestreams of liquid at the juncture points 18:.

Since manychanges can be made in the ap paratus disclosed, and manyapparently widely different embodiments of the invention can be madewithout departing from the scope of the claims, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative-and notin a limiting sense.

What is claimed is:

1 In gas and liquid contacting apparatus comprising a column with aliquid inlet and a gas outlet in the upper part thereof and a gas inletand liquid outlet in the lower part thereof, said column being adaptedfor countercurrent fiow, a packing for the column comprising a pluralityof vertically extending sheets disposed in the path of flow of said gasthrough the column, each sheet comprising straight slender elementswhich are vertically inclined and in contact, the elements beingarranged to form a plurality of mixing zones comprising a series ofintersections in spaced horizontal and spaced vertical rows, said rowsand said intersections being closely spaced; the distance therebetweenbeing suificient' to form spaces between the intersections large enoughto prevent capillary filming of the liquid thereacross.

2. In gas and liquid contacting apparatus comprising a column with aliquid inlet and a as outlet in the upper part thereof and a gas inletand liquid outlet in the lower part thereof, said column being adaptedfor countercurrent flow, a packing for the column comprising a pluralityof vertically extending sheets disposed in face to face contact and inthe path of flow of said gas through the column, each sheet comprisingstraight slender elements which are vertically liquid outlet in thelower partthereof, said column being adapted for countercurrent flow, apacking for the column comprising a plurality of vertically extendingsheets disposed in face to face contact and in the path of flow ofsaidgas through the column, each sheet comprising a network of straightslender elements which are vertically inclined and are regularlyarranged and in contact to form definite rows of quadrilateral meshes,each having diagonally opposed junction corners substantially verticallyaligned and defining liquid mixing and distributing zones respectively,the elements bounding each of said meshes diverging obliquely downwardlyin pairs from the upper junction corner of said latter mesh atsubstantially equal angles with the vertical, and converging towards thelower junction corner of said last-mentioned mesh at substantiallythe-same angle with respect to the vertical, said elements being soarranged that the mixing and distributing zones are closely spaced, thedistance therebetween being sufiicient to form meshes of a size toprevent capillary filming of the liquid thereacross. V

4. In gas and liquid contacting apparatus comprising a column with aliquid inlet and a gas outlet in the upper part thereof and a gas in-vlet and liquid outlet in the lower part thereof, said column beingadapted for countercurrent flow, a packing for the column comprising aplurality of vertically extending sheets disposed in face to facecontact and in the path of flow of said gas through the colunm, eachsheet com prising a network of obliquely extending slender elementswhich are vertically. inclined and are regularly shaped and regularlycriss-crossed to form definite vertical rows of equilateralquadrilateral, meshes of substantially the same size and shape, havingdiagonally opposite vertices in substantially vertical alignment, themeshes of one vertical row being staggered with respect to the meshes ofthe adjoining vertical row, and arranged in lattice relationshiptherewith to define a series of junction zones towards which theelements converge in pairs obliquely downwardly and from which theelements diverge in pairs obliquely downwardly, at least some of saidelements being in contact at the junction zones, said elements being soarranged that the junction zones are closely spaced, the distancetherebetween being sufficient to form meshes of a size to preventcapillary filming of the liquid thereacross.

5. In gas and liquid contacting apparatus com-- prising a column with aliquid inlet and ages outlet in the upper part thereof and ages inletand liquid outlet in the lower part thereof, said column being adaptedfor countercurrent flow, a packing for the column comprising a pluralityof vertically extending sheets disposed in face to" face contact and inthe path of fiow of said gas through the column, each sheet comprising afabric of straight slender packing elements which are verticallyinclined and are regularly arranged in accordance with a predeterminedpattern to form a network provided with a plurality of ver-i ticallyextending zig-zag sections having uniform alternate turns, and definingregular predetermined flow paths along which the liquid is adapted tofiow in definite streams respectively, these sections being joined atstaggered intervals to. define mixing zones where the streams merge and;

then subdivide as they descend, said elements being so arranged that themixing zones are closely: spaced, the distance therebetween beingsuffi-.

cient to form meshes of a size to-prevent capillary filming of theliquid thereacross.

6. In gas and liquid contacting apparatus com-. prising a column with aliquid inlet and a gas. outlet in the upper part thereof and a gas inletand liquid outlet in the lower part thereof, said column being adaptedfor countercurrent flow, a packing for the column comprising a pluralityof vertically extending sheets disposed in face to face contact and inthe. path of flow of said gas through the column, each sheet comprisingtwo or more criss-cross layers of slender packing elements ofpredetermined shape which are vertical- 1y inclined, the elements ofeach layer extending obliquely in the same general direction, and

. the elements of adjoininglayers extending obliquely in transversedirections to form a series of liquid mixing and distributingintersection zones, at least some of said elements being in contact atsaid zones, said elements beingso arranged that the liquid mixing anddistributing intersection zones are closely spaced, the distancetherebetween being sufficient to form meshes of a size to preventcapillary filming of the liquid thereacross.

7. In gas and liquid contacting apparatus comprising a column with aliquid inlet and a gas outlet in the upper part thereof and a gas inletand liquid outlet in the lower part thereof, said column being adaptedfor countercurrent flow, a packing for the column comprising aplurality, of vertically extending sheets disposed in face to facecontact and in the path of flow of said gas through the column, eachsheet comprising a plurality of straight elements which are verticallyinclined and are regularly arranged to form a series of intersectionsdefining liquid mixing and distributing zones, at least some of theinterthat the intersections are closely spaced, the distancetherebetween being sufiicient to form meshes of a size to preventcapillary filming of the liquid thereacross.

FRANCIS MsLvnL.

